Corrosion Protection Systems based on Lamellar Zinc Pigments

摘要

The anticorrosion properties of Zinc have been well-known for decade. Product development of a unique Zinc flakes morphology permitted to contemplate improved performances of Zinc Rich Primers to meet the increasingly stringent requirements of modem high-quality corrosion protection. By applying of a Bridge paint system, primers with Zinc Flakes, Intermediate coat and top coat, it was possible to obtain not only economic but also ecological advantages whilst maintaining the Bridge coating specifications. Zinc-rich coatings as the primary steel bridge corrosion protection system has, in the last 20 years, greatly increased the performance of painted steel in salt-rich environments. The mechanism of the zinc pigment as a sacrificial electrode is only effective by establishing contact between the zinc particles and the iron substrate. For optimal corrosion protection, however, the construction of a protective barrier layer is also important in addition to the cathodic protection. Talking these factors into account and particularly considering the different geometrical structures (zinc dust spherical, zinc flakes lamellar); it is possible to draw certain conclusions concerning the advantages and disadvantages of formulations using the individual pigments. Public opinion reacts more and more sensitively to pollution and all technical solutions have to be considered, so that a minimum amount of this "heavy metal" is used. The lamellar Zinc is one solution. Comparing a Zinc rich with a Zinc lamellar primer, the quantity of Zinc used in the latter is approximately one third. The lamellar structure of Zinc flakes with correspondingly higher binder is decisive for formulations with lower pigment concentration by volume (PVC) offering comparable or superior corrosion protection properties, with benefits in application (brushing , air and airless spraying , dipping and rolling) and coating properties 1. higher film, adhesion and cohesion 2. lower porosity and permeability (resistance to condensation) 3. smooth surface A comparative performances study against corrosion of three coating systems, each of them including a zinc rich epoxy primer based on spherical (dust), lamellar (flake) and a mixture of lamellar and spherical morphologies was conducted using the American Society for Testing and Material (ASTM) and the Society for Protective Coatings (SSPC) testing protocol. Result indicates a better zinc-rich paint system when using lamellar Zinc fora Category of C5-M exposure. Corrosion protection systems with lamellar zinc pigments are entirely comparable, by our testing for protective action, with the so-called zinc rich primers. Since they exhibit extraordinary advantages in respect of processing properties, priming, adhesion, condensate resistance and ease of repair, they provide a high-quality alternative.